Voltage Regulator Noise Cancellation Circuit Design

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Solution Overview

Problem

Traditional voltage regulators face challenges in effectively reducing noise generated by their own circuit elements, such as the reference voltage circuit and error amplifier, which limits their noise cancellation capabilities and stability due to large load capacitance and restricted noise reduction by the power supply rejection ratio (PSRR).

Innovation Solution

A voltage regulator design incorporating a noise cancellation circuit that connects to the reference voltage circuit and error amplifier, forming a closed-loop amplifier with a pass transistor and voltage divider to amplify and invert noise, allowing for effective cancellation of self-generated and power supply noise.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a low-pass filter is used to cancel noise from the reference voltage circuit, then noise is reduced, but the capacitor in the low-pass filter occupies a large area in a chip

Engineering Contradiction:

Improvenoise from reference voltage circuitVSAvoidcapacitor area in chip

Core Design Contradiction:

Object-affected harmful factorsVSArea of stationary object

Solution Approach 1:

The patent extracts the noise cancellation function from the traditional low-pass filter structure and implements it through a separate noise cancellation circuit that processes noise signals independently, allowing for more efficient noise reduction without requiring large capacitor areas

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the approach from passive filtering using large capacitors to active noise cancellation by injecting anti-phase noise signals, fundamentally changing the parameter of noise reduction from passive attenuation to active cancellation

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If a large load capacitance is used to filter noise from the error amplifier, then noise is reduced, but the stability of the voltage regulator is weakened

Engineering Contradiction:

Improvenoise from error amplifierVSAvoidstability of voltage regulator

Core Design Contradiction:

Object-affected harmful factorsVSStability of the object's composition

Solution Approach 1:

The patent implements a feedback mechanism where the noise cancellation circuit continuously monitors and processes noise signals from the error amplifier, injecting anti-phase signals to cancel noise while maintaining system stability through controlled feedback rather than relying on large load capacitance

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent introduces an intermediary noise cancellation circuit between the error amplifier and the output stage, which acts as a mediator to filter noise without requiring large load capacitance, thus preserving system stability

Inventive Principle:

Principle #24Intermediary (Mediator)

3Object-affected harmful factors

If the error amplifier is used to reduce noise from input voltage through PSRR, then noise reduction is achieved, but the noise reduction is restricted by the gain and bandwidth of the error amplifier

Engineering Contradiction:

Improvenoise from input voltageVSAvoidnoise reduction capability limited by gain and bandwidth

Core Design Contradiction:

Object-affected harmful factorsVSAdaptability or versatility

Solution Approach 1:

The patent segments the noise reduction function into two independent paths: the traditional PSRR path through the error amplifier and a new dedicated noise cancellation path, allowing each path to operate independently without being constrained by the gain and bandwidth limitations of a single amplifier

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS10146239B2Voltage regulator with noise cancellation function

Publication Date: 2018.12.04 REALTEK SEMICON CORP

AI summary

Disclosed is a voltage regulator. The voltage regulator includes a reference voltage circuit, a noise cancellation circuit, an error amplifier, a pass transistor and a voltage divider. The voltage regulator can cancel the noise generated by the reference voltage circuit and the error amplifier, and also can improve its Power Supply Rejection Ratio (PSRR).